Cutter for rotary boring-drills.



H. R. HUGHES.

CUTTER FOR ROTARY BORING DRILLS.

APPLICATION FILED FEB. 24. 1914.

1 143371, v, Patented June 15, 1915.

PAT nice,

HOWARD B.

:auenss, or noos'ron, 'rnxas, ASSIGNOR m snanr-n 'uenns TOOL COMPANY, or HOUSTON, TEXAS, A CORPORATION or TEXAS.

CUTTER FOB ROTARY BORING-DRILES.

iam

Specification of Letters Patent.

Patented June 115, 11915.

Applieation-filed lebruary 24, 1914. Serial no. 820,676;

To all whom it may concern Be it known that I, HOWARD R. Hoenns, a citizen of the United States, residing at Houston, Texas, have invented a certain new and useful Improvement in Cutters for Rotary Boring-Drills, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertainsto make and use the same.

This invention relates to rotary boring drills of the type illustrated in my prior Patent No. 930,759, dated August 10, 1909, in which the cutting means consists of approximately frusto-conical-shaped cutters that are mounted on the head of the drill in such a manner that their axes of rotation are inclined downwardly and inwardlv toward the longitudinal center of the drill head.

In developing and perfecting the type of drill illustrated in my prior patent abovereferred to I formed the cutting surfaces on the cutters in various ways with a view of obtaining an efiicient cutting surface of great area that would not wear away quickly when the drill was in use, and after numerous exhaustivev tests I adopted as a standard construction a substantially frustoconical-shaped cutter whose cutting surface is composed of chisel-teeth that radiate from the inner end or small end of the cutter in substantially the manner illustrated-in my said prior'patent. While a cuttinflg surcient face of the character mentioned is e in that the chisel-teeth obtain a firm grip on the bottom of the hole being formed, the

objectionable feature of such a cutter is that the outer end portions of the chisel-teeth which act on the outer portion of the bottom of the hole, wear down quickly on account of the relatively greater amount of work that these portions of the teeth have to do, owing to the fact that the zone on which they act is of greater diameter than the zone on which the remaining portion or inner portion of the teeth act. In other words, the inner half of the chisel-teeth travel over a circular zone of much less diameter than the circular zone over which the outer half of the chisel-teeth travel, and as the number of chisel-teeth in the outer half of the cutter is the same as the number of chisel-teeth in the inner half of the cutter the outer half of the chisel-teeth naturally wear down faster than the inner half of the teeth. Furthermore, the cutting edges of the teeth in the outer half of the cutter are spaced farther apart than the cutting edges of the teetli in the inner half of the cutter, notwithstanding the fact that the outer lialf of the teeth out an area of much greater diameter. The result is that the outer end portions of the chisel-teeth on an approximately frusto-conical-shaped' cutter Wear away more quickly than the remaining portion of the teeth, thereby causing the outer portion of the cutter to merely rub on the bottom of the hole Without cutting same, and, consequently, preventing the unworn portions of the teeth from acting efliciently or from disintegrating the material as effectively as they would if the outer portion of the cutter did not rub on the bottom of the hole. In large cutters this action is more pronounced, and, furthermore, there is a tendency for the outer end portions of the of the iii- 3th are deeper than the inner end portions of the teeth. r

The object of my present invention is to overcome the objectionable features abovementioned and produce an efiicient frustoconical-shaped cutter whose outer end portion will not Wear down quickly, and to this end I have devised a cutter which is provided at its outer end portion with a cutting surface that consists of a plurality of spiral teeth or a continuous tooth that extends spirally around the cutter a number of times, the cutting surface on the inner end portion of the cutter'preferably consisting of radially-disposed chisel-teeth, shar pointed projections, or any other suitab e type of cutting surface that Wlll insure the cutter obtaining a firm grip on the bottom of the hole. By constructing the cutter in this manner I not only greatly increase the area of the cutting surface and provide an exceptionally large cutting surface where it is most needed, but I eliminate the tendency of the cutter to break, especiall in large cutters, and I reduce the cost 0 manufacturing the cuttter. 1

Figure 1 of the drawings is a side elevational view of a rotary boring drill equipped with. cutters constructed in accordance w th my invention, one of the cutters bemg broken away; and Fig. 2 is a side elevational view, partly broken away, of a cutter embodying my invention but constructed-in a different manner Fig. 1..

Referring to Fig. 1 of the drawings, A designates the head of the drill, and B designates two approximately frusto-conicalshaped cutters rotatably mounted on said head in such a manner that their axes of retation incline downwardly and inwardly toward the longitudinal axis or vertical center of the drill head. The portion of the cutting surface of'each of the cutters B which acts on the outer portion of the bottom of the hole, namely, that portion of the bottom of the hole which is located adjacent the side wall of the hole, consists of a continuous spiral tooth 1 that extends a number of times around the cutter, and the remaining portion of the cutting surface of the cutter that acts on the bottom of the hole is made up of a plurality of radiall -disposed chiselteeth 2,. said radially-disposed chisel-teeth either being plain orprovlded with notches 2, as herein shown. Each of the cutters B is preferably provided at its base end with an oppositely tapered or beveled portion that has chisel-teeth 3, or i type of cuttingsurface, for removing the as to maintain suflicient clearance for the drill head. When the drill is in operation the chisel-teeth 2 on the cutters B cut and disintegrate the material at the center portion of the bottom of the hole, and the spiral teeth 1 on said cutters cut and disintegrate the material at the outer portion of the bottom of the hole, the chisel-teeth 2 insuring sufiicient traction to prevent slipping of the cutters.

In order to emphasize the superiority of a cutter of the construction above-described over a cutter that is merely provided .with straight chisel-teeth that extend radially from the small end of the cutter to the base of the cutter, I will state that in a cutter of the typeherein shown, designed for use on a 15" drill, the length of the cutting edge of the continuous spiral tooth -1 is approxito mately 144" when said tooth extends around the cutter five times; whereas, in a cutter of the same size rovided with radially-disposed chisel-teet that extend to the "base the.

combined length of the portions of the chisel-teeth w ich cover a corresponding portion of the cutter is only approximately 59". In other words, b forming a continuous spiral tooth on t e outer end or-. tion of the cutter, or on the portion 0 the 60 cutter which acts on "the outer portion-of the bottom of the hole, instead of having the chisel-teeth 2 extend clear across the. face of the cutter, I obtain nearl thr as great a cutting area.

of manufacturing a cutter of the con from the cutters shown in portion of the cutter any other suitable.

material from the side wall of the hole so 39. T e cost.

herein illustrated and described is less than the cost of manufacturing a cutter equipped with radiallydisposed chisel-teeth that extend clear across the face of the cutter because less work is require on a milling machine; and another desirable feature of such a cutter is that the outer portion of same is stronger and less liable to struction 'break owing to the fact that the material in same is not cut away to form deep notches between the radially-disposed chisel-teeth, as in the cutters of this general type heretofore in use.

The cutter can either be formed in the manner shown in Fig. 1 wherein the two oppositely tapered portions of same merge into each other and thus form a hole with a sharp angle or corner at the junction of the bottom and side wall of the hole, or, if desired, the cuttercan be provided with a cyli'ndrical-sha'ped cutting portion 4 arranged intermediate the oppositely tapered base that acts on the side wall of the hole and the outer portion of the cutter upon which the spiral tooth 1 is formed, so as to. form a hole whose side wall which act on the side wall and on the bottom of the hole.

From the foregoing it will be seen that the complete cutting surface of my improved cutter is made up 'of a portion a: that acts on the side wall of the hole, a portion 3 formed by a continuous s iral tooth on the base part of the frusto-comcal-shaped portion of the cutter that acts on the outer ortion of the bottom of. the hole, preferably made up of chisel-teeth on ter that acts on the portion of the bottom of the hole which lies inside of the 'zone or path of the portion 3 of'the cutter. The

A cutter of. the construction"-previous ly-- described be used for a long period w thout withdrawing it from the hole,

' owing to the fact that the portion of same and a portion 2 which is radially-disposed the apex portioniof the cut-' length .of the cutting-edge on the portion 3 D that does not track, the Y which has the greatest area to cut is provided with a cutting surface of proportion ately greater area than the remaining portion of the cutting surface which acts on the bottom of the hole, and which will not of the fact that the spiral tooth on same can be produced in an automatic machine.

and at a lower cost than it would be pos sible to mill chisel-teeth in this portion of the cutter; and, furthermore, the cutter 1s exceptionallystrong because very little material is removed from the outer portion of same during the operation of forming the continuous spiral tooth 1 on the cutter. ile I prefer to provide the inner end portion of the cutter with chisel-teeth, the spiral teeth 1 could, of course, be continued around the inner end portion of the cutter to the apex of same.

Having thus described my invention, What claim as new and desire to'secure by Letters Patent is:

1. Acutter for rotary boring drills having a substantiallyfrusto-conical-shaped cutting surface whose base portion consists of a continuous spiral tooth and Whose apex portion is provided with a cutting surface Whose cutting portions extend at approximately right angles to said spiral tooth so that they will obtain a firm hold on the material lying inside of the zone on which said spiral tooth acts.

2. A substantially 'frusto-conical shaped cutter for rotary boring. drills provided at its base end with a continuous spiral tooth that extends a number of times around the cutter, and provided on its apex portion with a cutting surface that comprises cutting portions which form substantially radially disposed cuts in the material at the bottom of the hole lying inside of the zone on which said spiral tooth acts.

3. A rotatable cutter for rotary boring drills provided with a substantially frustoconical-shaped portion that has projections on'the apex portion of same arranged in radiallydisposed rows, and a spiral cutting edge on the base portion of same.

4. A rotatable cutter for rotary boring drills provided with a substantially frustoconical-shaped portion that has chisel-teeth on the apex portion of same, and a spiral cutting edge on the base portion of same, said cutter also having an oppositely tapered cutting portion that acts on theside wall of the hole being formed. v

5. A substantially frusto-conical -shaped cutter for rotary boringdrills provided at its base end with a cutting surface for acting on the side wall of the hole, a spiral formed in cutting edge on said cutter which acts on the outer portion of the bottom of the hole, and a cutting surface of a different character on the apex portion of the cutter which acts on the material lying inside of the zone on the bottom of the hole on which said spiral cutting edge acts.

6. A substantially frusto-conical-shaped cutter for rotary boring drills provided at its base end with a cutting surface for acting on the side Wall of the hole, a spiral cutting edge on said cutter which acts on the outer portion of the bottom of the hole,

and radially-disposed chisel-teeth on the apex portion of the cutter.

7. A substantially frusto-conical-shaped its base end with a cutting surface for acting on the side wall of the hole, a spiral cutting tooth extending around the base portion ofthe cutter which acts on the outer portion of the bottom of the hole, and radially-disposed chisel-teeth extending from said spiral tooth; .to the apex of the cutter, said chisel-teeth having notches the cutting edges of. same.

8. A cutter for rotary boring drills provided With a substantially frusto-conical-shaped portion that acts on the bottom of the hole, and an oppositely tapered cutting portion that acts on the side wall of the hole, the large part of said frusto-conical-shaped portlon having a spiral cutting edge that ex-' and the apex tends around and around same, portion of same being provided with a cutting surface that comprises cutting portions that extend at approximately right angles to said spiral cutting edge so as to obtain a firm grip on the bottom of the hole.

9. A cutter for rotary boring drills provided with a substantially frusto-conicalshaped portion which is provided with a spiral cutting edgethat acts on the material at the outer portion of the bottom of the hole, and a cutting surface on said cutter formed by radially disposed chisel teeth whose outer ends terminate at the portion of the cutter on which said spiral cutting edge is formed.

10. A cutter for rotary boring drills procutter for rotary boring drills provided at vided with a substantially frusto-conicalshaped portion that acts on the bottom of the hole, and an oppositely tapered portion having chisel-teeth that act on the side wall of the hole, said frusto-conical-shaped portion having aspiral tooth that extends around and around same adjacent the base portions of different lengths,

, spiral cutting e ing'jround the base end of same, aly the greatest len h being prising an approximately frustoconicalon having a spiral tooth extendand radi- {disposed chisel-teeth, on the apex end shaped port of same, a cylindrical-shaped cutting porchisel-teeth that act on head, each of" said cutters being provided tooth that acts on the tion at thebase of said conical-shaped portion which is provided with chisel-teeth, and an oppositely tapered portion provided with the side wall of the hole. I

l3. A rotary borinigTirill consistingK of a head, substantially sto conical s aped cutters on said head whose axes of rotation are inclined downwardly and inwardly toward-the longitudinal axis or centerof the with -a spiral cutt in outer portion of the ottom of the hole, and radially-disposed chisel-teeth that terminate at said spiral tooth and portion of .the bottom of the hole that lies inside of the zone on which said spiral tooth head, substantially frusto-conical-shaped cutters on said head whose axes of rotation are inclined downwardly and-inwardly toward each of said cutters being which act on the cts. side: Wil of the 14. A rotary boring'drill-consisting of a radiall -disposed chisel-teeth that terminate at sai spiral tooth and which act on the portion of the bottom of the hole that lies inside of the zone on which said spiral tooth acts, and cutting thus maintain sufficient clearance for the drill head. r

15. A cutter for. rotar boring drills consisting of a 'substantia ly frusto-conicalsurfaces on said cutters which act on the side wall of the hole and shaped member provided on its outer surface "with a cutting tooth around said member a number of times and also having aseparate and dlstinct cutting surface of a different character which comth t extends P F y prisesa plurality of substantiallyradiallydisposed teeth that insure a firmgrip of the cutter on the bottom of the hole.

'16; A cutter for rotary boring drills consisting. of a substantially shaped member whose base ortion is provided with a continuous toot that extends spirally around said member and whose apex portion is provided with a cutting Sll1-' face of a different character'whose cutting edges are disposed at approximately right v angles to said 'sitelyl tapered spiral tooth, and'an oppoportion at the base end of said memberwhiclll puts the material on the In tstimon whereof- I hereunto aifix my signature in t e presence of two witnesses, th s lg'f day of February 7 2i flOWARD Witnesssz. s

HARRY'B. HAGENOT, i E.,lilLWmeurr.

frusto conical- 

